1. Field of the Invention
This invention relates to selected conductive compositions containing silver and silver chloride which are particularly useful for fabricating into human contact electrodes.
2. Brief Description of the Prior Art
Human contact electrodes, especially those used for measuring cardiovascular activity, have been made by applying (e.g. electrodepositing) a conductive film of metallic silver and silver chloride onto a tab-like substrate. The coated substrate is then affixed with a suitable adhesive by which the tab-like substrate (i.e. electrode) will maintain contact with the human body
In taking a human cardiovascular reading, an electrode is affixed to a desired position of the human chest and an electrical connection is also attached to the electrode from an electrocardiogram (EKG) machine.
One problem with prior silver/silver chloride electrodes is that they may not work for at least 30 seconds after defibrillation electrical charge or shock was applied to a human chest. During that time, medical personnel will be unable to monitor the activity of the heart. This period of unoperability is caused by polarization of the electrode due to the defibrillation electrical charge.
The invention disclosed in U.S. Pat. No. 4,877,512, which issued to Richard E. Bowns and David L. Diepholz on Oct. 31, 1989, presented a commercially viable solution to that problem. This U.S. patent is incorporated herein by reference in its entirety. While the silver/silver chloride compositions disclosed in this patent were superior to the prior art silver/silver chloride compositions, the vinylidene chloride thermoplastic polymer used therein lacked high temperature (i.e., above 250.degree. C.) thermal stability and long-term shelf life necessary for all types of application modes of the composition onto a substrate. Silver/silver chloride compositions, having a polyurethane thermoplastic resin, are also known for this use; however, they are also believed to lack high temperature thermal stability and long-term shelf life. Accordingly, there is a need for silver/silver chloride composition having better high temperature thermal stability and shelf life properties than the compositions disclosed in U.S. Pat. No. 4,877,512. The present invention is a solution to that need.